Quasi-invariant Gaussian measures for the two-dimensional defocusing cubic nonlinear wave equation

Abstract

We study the transport properties of the Gaussian measures on Sobolev spaces under the dynamics of the two-dimensional defocusing cubic nonlinear wave equation (NLW). Under some regularity condition, we prove quasi-invariance of the mean-zero Gaussian measures on Sobolev spaces for the NLW dynamics. We achieve this by introducing a simultaneous renormalization of the energy functional and its time derivative and establishing a renormalized energy estimate in the probabilistic setting.